1. Field of the invention
The present invention is generally concerned with clutch release bearing control yokes as used in particular in automotive vehicles.
2. Description of the prior art
As is well-known a clutch release bearing is designed to actuate the clutch release device of a clutch mechanism when the clutch release bearing is actuated by a control member usually referred to as a yoke. To this end, it generally comprises an actuator member which acts on the clutch release device and an operating member on which the control yoke acts, the actuator member being axially coupled to the operating member which comprises a transversely disposed bearing member for the control yoke to act on. This comprises a flange, which may be subdivided into two or more radial arms.
The clutch release bearing control yoke usually comprises a pivot section around which it pivots when actuated by a control arm and an operative section which is adapted to act axially on the clutch release bearing at two points thereon which are substantially diametrically opposed.
The control arm of this kind of control yoke may be integral with it, for example, the two being formed as a single component. This is usually the case when the support for the control yoke is of the ball and socket type.
As an alternative, the control yoke control arm may be separate to the control yoke. In practice, this is the case when the control yoke support is a pivot shaft, in which case the control arm and the control yoke may be moved apart along the pivot shaft and the control arm may extend at an angle to the shaft which is different to that for the control yoke.
Be that as is may, the control yoke control arm is designed to be coupled by a transmission system to a clutch pedal and, in order to act on the clutch release bearing at two points thereon which are substantially diametrically opposed, the operative section of the control yoke comprises two areas referred to hereinafter for convenience as bearing areas.
In practice, these bearing areas on the control yoke through which it acts on the clutch release bearing are usually formed at the ends of respective fingers, which together constitute the operative section of the control yoke.
At the present time these two fingers are usually rigidly connected together in a continuous manner to form a single part which is generally U-shaped in configuration.
The present invention is more particularly, but not exclusively, concerned with the case there the clutch release bearing is of the "pull" type, that is to say designed to apply traction to the clutch release device of the clutch mechanism, having part of its actuator member engaged behind the clutch release device.
For these clutch release bearings, the flange of the operating member on which the control yoke acts is spaced at some distance from the associated actuator member so that the operative section of the control yoke can apply traction to the flange, that is to say a force from the side of the latter towards the actuator member.
One of the problems to be overcome when assembling these "pull" type clutch release bearings results from the fact that this operation involves relative engagement of the clutch release bearing and the control yoke, the operative section of the latter having to be engaged transversely between the flange on the operating member of the clutch release bearing and the actuator member thereof.
In other words, the operative section of the control yoke must be engaged behind the transverse flange of the operating member of the clutch release bearing.
In the case of a "pull" type clutch release bearing supported by the clutch mechanism, part of its actuator member is engaged behind the clutch release device thereof. The control yoke is usually independently mounted on the casing of the gearbox, pivoting around a fixed support by virtue of its pivot section, this fixed support comprising a transverse shaft or ball and socket joint supported by the casing.
Thus, during the relative axial movement towards one another of the gearbox casing and the clutch mechanism, which is usually supported by the casing of the engine, it is necessary to progressively engage the operative section of the control yoke behind the transverse flange of the operating member of the clutch release bearing.
This operation involves offering up the control yoke in a position which is initially substantially flat or horizontal, the control yoke being progressively moved to a more vertical position as its operative section is engaged behind the transverse flange of the operating member of the clutch release bearing. This is a difficult operation, particularly when the control yoke is pivoted by means of a ball and socket connection, in view of the additional degrees of freedom in respect of its movement.
This operation may even prove impossible, as the pivoting movement of the control yoke necessary to move it to a vertical position requires a non-negligible dead space which is not always available.
To overcome this difficulty, it has been proposed to first mount the clutch release bearing on the control yoke, before mounting the clutch release bearing on the clutch release device of the clutch mechanism. Then, when moving the casing of the gearbox and the clutch mechanism axially closer together, the clutch release bearing is automatically "snapped" onto the clutch release device of the clutch mechanism, working blind.
The arrangements used for this purpose do not favor subsequent dismantling, however.
It has been proposed to engage the control yoke transversely on the clutch release bearing, after the relative axial movement towards one another of the gearbox casing and clutch mechanism, without the control yoke being mounted on the casing beforehand.
This solution is not acceptable in practice unless the support for the control yoke on the gearbox casing is external to the casing.
If this support is a ball and socket joint, it is still acceptable for the ball and socket joint to be inside the gearbox casing. In practice, however, the control yoke must then be formed with an opening to permit its engagement on the ball and socket joint, in the vicinity of the housing with which it must cooperate. This is prejudicial to the mechanical strength of the control yoke.
It has been further proposed to provide a pivoting, bayonet or quarter-turn type mounting of the clutch release bearing on the control yoke.
In practice, this solution is suited only to vehicles where the gearbox casing is readily accessible.
In the case of touring automobiles the necessary space is not always available.
German patent application No. 29 35 079 proposes subdividing the control yoke into two separate parts, to be pivoted together scissors-fashion.
This scissors type pivoting means that the parts must overlap one another at the pivot point, however.
This is practicable only if the parts are flat, but they then have insufficient stiffness in the axial direction, perpendicular to their plane, this being the direction in which they act on the clutch release bearing.
If they are of channel section, in order to increase their stiffness, it becomes difficult to overlap them at the pivot point, unless they are asymmetrical. In this case, they would not have the same stiffness and they would not act equally on the clutch release bearing, having an overall detrimental effect.
A general objective of the invention is to provide a device which overcomes the aforementioned disadvantages in providing a very simple solution to the problems discussed.